ORANGE COUNTY, CA (Gray News) - Health officials in Orange County, CA, are warning moviegoers who attended a midnight screening of “Avengers: Endgame” that they may have been exposed to measles.

Before realizing she was sick, a woman in her 20s attended a midnight screening of the “Avengers” blockbuster on Thursday at an AMC movie theater in Fullerton, CA, CNN reports. Health officials say she was at the theater from 11 p.m. to 4 a.m.

Everyone who was in the building, not just those at the “Avengers” screening, may have been exposed to the contagious disease.

The woman also went to her Santa Ana, CA, workplace for a few days and to the St. Jude Emergency Department in Fullerton, the Los Angeles Times reports.

The measles case is the first confirmed in Orange County in 2019. The woman had recently traveled to a foreign country with an outbreak of the disease, according to the Orange County Health Care Agency.

Health officials say the woman was considered infectious between April 23 and May 1. After realizing she was sick, she voluntarily isolated herself at her Placentia, CA, home.

'Avengers: Endgame' is already the highest-grossing movie of the year

Last week, more than 1,000 students and staff members at two Los Angeles universities were quarantined on campus or sent home after county officials declared a measles outbreak, according to the Associated Press.

The Centers for Disease Control and Prevention has confirmed 704 cases of measles across the country, making this the nation’s worst year for the disease since 1994.

The vaccine became available in the 1960s and is considered safe and highly effective. Because of it, measles was declared all but eliminated in the U.S. in 2000, but the disease has experienced a resurgence in recent years.

This trip, the first of two President Donald Trump is expected to make to Japan in the next six weeks, is more of a social call meant to highlight the alliance between Japan and the United States and the friendship between their leaders.